Carbazole-based 1D and 2D hemicyanines: synthesis, two-photon absorption properties and application for two-photon photopolymerization 3D lithography

One and two dimensional (1D and 2D) carbazole based hemicyanines, where methyl pyridinium, methyl indolium and methyl benzothiazolium were used as acceptor group, were synthesized by Knoevenagel condensation. One-photon absorption, fluorescence and two-photon fluorescence spectra were investigated. The experimental results indicated that the different ionic acceptors affect their one-photon and two-photon properties. Among them, 2D methyl pyridinium carbazole derivatives exhibited low quantum yields and large two-photon absorption cross sections more than 1600 GM. The synthesized compounds were used as photoinitiator of two-photon photopolymerization (TPP), and three-dimensional (3D) microstructure was successfully fabricated by TPP 3D lithography. They could be utilized as effective two-photon polymerization photoinitiators.